Products containing cyanoacrylate are quite active chemically. Because of the reactive nature of cyanoacrylates, it has been difficult to find packaging means and materials with which the cyanoacrylate product does not interact in a way which is detrimental to the cyanoacrylate in the package, and to holding it in the package.
Traditionally, cyanoacrylate adhesives have been packaged in plastic bottles and metal tubes. The plastic containers do not provide adequate vapor barrier, such that the shelf life of products packaged in conventional plastic containers is undesirably short. Metal tubes also have some undesirable characteristics. They are relatively inflexible such that they can be flexed only a few times as in repeated dispensing before cracks develop in the tube sidewall. Overall, though, shelf life of cyanoacrylate products is better in metal tubes than in plastic, at least until the tube is initially opened. Nevertheless, the shelf life, even in metal tubes, is less than desired. Clearly, cyanoacrylates are readily identified as being difficult to hold in a package over a desirable shelf life period.
Products have been packaged in tube-type containers of generally three types. The first type is a metal tube. Such tubes provide excellent barrier properties, but have undesirable functional properties as discussed above. The second type is a plastic tube made from either single or multiple layers of plastics. While plastic tubes may be excellent for many products, no plastic packaging materials are known which are excellent for holding cyanoacrylate-type products. The third type is a tube made from previously formed multiple layer sheet materials containing a layer of metal foil and a plurality of layers of plastic materials, generally referred to hereinafter as laminated tubes.
The third type of tube container has been used conventionally for holding hygienic-type products such as toothpaste. Toothpaste is chemically quite active, and is generally considered difficult to hold in a package.
Attempts to package cyanoacrylate adhesives in the third type of tube containers were not successful with any of the conventionally known sheet materials used to make the laminated tubes. After being packaged in conventional tubes of the third type, the cyanoacrylate adhesive migrated through polymer layers to the foil layer. The tube delaminated between the foil layer and the adjacent polymer layer. The delaminated tube was not satisfactory for the package.
Cyanoacrylate also tends to cause swelling of the polymers. In trials with some experimental multiple layer tubes, polymer layers disappeared as distinct layers, presumably having been either dissolved into the cyanoacrylate or otherwise absorbed into it.
It is an object of this invention to provide a packaging sheet material capable of holding cyanoacrylate-type products.
It is another object of this invention to provide such a sheet material which has excellent barrier to passage of matter through the sheet material.
It is yet another object to provide a package capable of holding a cyanoacrylate-type product.